纳米颗粒分布对镁基复合材料强化机制的影响

Influence of nano particle distribution on the strengthening mechanisms of magnesium matrix composites

Orowan强化、热错配强化和Hall-Petch强化是纳米颗粒增强镁基复合材料的主要强化机制,纳米颗粒在基体中的分布状态对起主导作用的强化机制具有重要影响。本文中对现有强化机制模型进行了适当修正,以纳米SiC颗粒增强AZ91D复合材料为例,通过理论计算分析了纳米颗粒完全分布于晶内、完全分布于晶界、在晶内晶界上均有分布的三种状态对镁基复合材料屈服强度的影响,并与实验结果进行对比。结果表明:颗粒完全分布于晶内时,增强效果最好,主要增强机制为Orowan强化;颗粒完全分布于晶界上时,增强效果最差,主要增强机制为Hall-Petch强化。颗粒在晶内晶界上均有分布时,多种强化机制共同发挥作用,增强效果随着晶内与晶界上颗粒比例的减小而逐渐减弱。

Orowan strengthening,thermal mismatch strengthening and Hall-Petch strengthening are known as the main strengthening mechanisms of nano particle reinforced magnesium matrix composites.However,the distribution of the particles in the matrix has an important influence on the enhancement effect and determines the dominant mechanism.In this paper the existed strengthening models were modified.The influence of three types of nanoparticle distribution,intragranular,grain boundary and intragranular-boundary distribution,on the yield strength of the nano SiC particle reinforced AZ91D composites was analyzed based on the modified models.The calculated results were compared with the experimental results.The results show that the composite has the best strengthening effect when the particles are completely distributed within the grain and the dominant mechanism will be Orowan strengthening;the composite shows the least strengthening effect while the particles are fully distributed along the grain boundary and the main mechanism will be Hall-Petch strengthening;the multi strengthening mechanisms will work when the particles are distributed both in the grain and on the grain boundary,in which case the strengthening effects will be weakened as the proportion of the fraction of the particle inside the grain to that on the grain boundary decreases.